fix: add omitempty to dashboard spec json field and generate docs

[HVBE]

Description

• adds omitempty to dashboard.spec.json
• regenerates api-docs
• fixes misplaced comments in structs, adding descriptions where they aren't supposed to be
• Set serviceAccountName: grafana-operator-controller-manager

Relevant issues/tickets

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• This change requires a documentation update
• I have added tests that prove my fix is effective or that my feature works
• I have added a test case that will be used to verify my changes
• Verified independently on a cluster by reviewer

Verification steps

[HVBE]

Partially addresses comments from #596

[NissesSenap]

LGTM
I will also add that you are setting:
serviceAccountName: grafana-operator-controller-manager
in the description.